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Appl. Environ. Microbiol., Sep 1997, 3577-3584, Vol 63, No. 9
G Dong, C Vieille and JG Zeikus
The gene encoding the Pyrococcus furiosus hyperthermophilic
amylopullulanase (APU) was cloned, sequenced, and expressed in Escherichia
coli. The gene encoded a single 827-residue polypeptide with a 26-residue
signal peptide. The protein sequence had very low homology (17 to 21%
identity) with other APUs and enzymes of the alpha- amylase family. In
particular, none of the consensus regions present in the alpha-amylase
family could be identified. P. furiosus APU showed similarity to three
proteins, including the P. furiosus intracellular alpha-amylase and
Dictyoglomus thermophilum alpha-amylase A. The mature protein had a
molecular weight of 89,000. The recombinant P. furiosus APU remained folded
after denaturation at temperatures of < or = 70 degrees C and showed an
apparent molecular weight of 50,000 in sodium dodecyl
sulfate-polyacrylamide gel electrophoresis. Denaturating temperatures of
above 100 degrees C were required for complete unfolding. The enzyme was
extremely thermostable, with an optimal activity at 105 degrees C and pH
5.5. Ca2+ increased the enzyme activity, thermostability, and substrate
affinity. The enzyme was highly resistant to chemical denaturing reagents,
and its activity increased up to twofold in the presence of surfactants.
Copyright © 1997, American Society for Microbiology
Cloning, sequencing, and expression of the gene encoding amylopullulanase from Pyrococcus furiosus and biochemical characterization of the recombinant enzyme
Department of Biochemistry, Michigan State University, East Lansing 48824, USA.
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